The invention is directed to an angle measurement with a graduation carrier which is connectable to a shaft by a hub, and which is scanned by a stationary scanning arrangement, installation means being provided for defining the positional correlation of the graduation carrier and scanning arrangement.
Such angle measurement apparatus are also designated as "built-in rotary encoders", which comprise no support of their own (for instance company publication of the DR. JOHANNES HEIDENHAIN GmbH, Traunreut: Rotary Encoder, issued 2/88).
A preassembled angle measurement device without its own support is known U.S. Pat. No. 4,689,595. In a preassembled state, a clamping spring causes the cohesion of the scanning arrangement with the hub to which the graduation carrier or support is fastened. A stop is provided at the hub, which contacts the scanning arrangement during the preliminary assembly and which fixes the hub in the radial and the axial direction. In this state the angle measurement apparatus is placed on the drive shaft and the scanning arrangement is fastened at the mounting surface of the drive unit. Subsequently, the clamping spring is moved out of engagement and the hub is shifted in the axial direction onto the drive shaft. This shift is required in order to cancel the contact of the stop of the hub with the scanning device and in order to assure a friction-free rotation of the hub relative to the scanning arrangement.
In this angle measurement apparatus there exists, in the preassembled state, a defined correlation between the hub and the scanning device in the radial and axial directions with respect to the hub axis, this correlation must however be removed during the installation at the drive unit. Because of the required axial displacement of the hub and of the graduation carrier relative to the scanning device, no defined correlation can be achieved without additional auxiliary means, and indeed neither in the radial nor in the axial direction. The measures disclosed in the U.S. Pat. No. 4,639,595 assure only security during transport.
Additional angle measurement devices are described in the U.S. Pat. No. 4,556,792 and German Offenlegungsschrift 37 40 744. Expensive adjustment instruments are required for the axial and radial adjustment of the hub with respect to the scanning device. The fixation of the hub with respect to the scanning device occurs by means of a plurality of elements, which must all be laboriously removed by the recipient which requires a great deal of time.